The invention relates to the reconstruction of a tridimensional image of a moving object, in particular moving with a substantially cyclic motion.
The invention finds a particularly interesting application in the medical field, in which the reconstruction of the internal structures of patients under examination, in particular the reconstruction of images of vessels of the heart, is undertaken.
The invention can however find applications in other fields, especially in industrial non-destructive testing in which examinations of the same type as medical examinations are carried out.
The tridimensional reconstruction of images is generally performed on the basis of bidimensional projected images of the object. However, difficulties arise in this image reconstruction when the object is moving, as is the case for the heart.
Another difficulty encountered in the reconstruction of tridimensional images on the basis of bidimensional images resides in the difficulty of matching between the images, that is to say of being able to tag with minimum error the same elements of the object, for example certain vessels, from one image to another. The difficulty is further increased here owing to the movement of the object, for example the heart.
Certain reconstruction techniques require the intervention of the user, in this instance the doctor, to solve the matching problems more easily.
The invention proposes a fully automatic reconstruction of images of a moving object, and which requires minimum, or even zero interaction with the doctor.
In an embodiment of the invention proposes a process for reconstructing a tridimensional image of an object moving with a substantially cyclic motion, for example the vessels of the human heart, in which, for an acquisition duration extending over several cycles of the movement of the object, an acquisition of a plurality of initial digital radiographic images is performed using a snapshot apparatus rotating around the object. Initial images having the same temporal occurrence in the course of each cycle are selected respectively in successive cycles in such a way as to form a group of images which is associated with this same temporal occurrence. Several different groups of initial images corresponding respectively to several different temporal occurrences are formed. An intermediate tridimensional representation of the object is reconstructed on the basis of each group of initial images and of an iterative image reconstruction algorithm. A law of spatial deformation between two intermediate tridimensional representations is formulated on the basis of the two intermediate tridimensional representations corresponding to two successive temporal occurrences, and a final tridimensional representation of the object is reconstructed on the basis of the initial images successively acquired, of the spatial deformation laws successively formulated and of an iterative image reconstruction algorithm.
An embodiment of the invention makes it possible ultimately to obtain a tridimensional representation of the object which takes its movement into account. The user, in this instance the doctor, can then easily be provided, on his screen, with a projected bidimensional image of this object on the basis of the final tridimensional representation obtained. Moreover, given that successive laws or models of spatial deformation corresponding to different temporal occurrences have moreover been formulated, it is also possible to provide the user, for example the doctor, with projected bidimensional images of the object, and especially of certain vessels, at successive time instants.
Stated otherwise, the process according to the invention allows the reconstruction of an image in xe2x80x9cfourxe2x80x9d dimensions, namely a tridimensional image furthermore assigned a time parameter.
The selection, in the successive cycles, of the images having the same temporal occurrence can be performed by using an auxiliary control signal representative of the cyclic motion of the object. Thus, it will be possible to use a physiological signal such as for example an electrocardiogram representative of the movement of the heart and making it possible to determine accurately the cycles of the cardiac movement.